Method and apparatus for the electrolytic coating of metal strip



Feb. 15, .1949. E. T. LORI 2,461,556

METHOD AND APPARATUS FOR T ELECTROLYTIC I l I COATING OF METAL STRIP Filed April 1, 1943 6 Sheets-Sheet 1 @v Q 7 l INVENTOR. 50m 2102 6,

1X6 UTTOENQ.

Feb. 15, 1949.

ORIG 2,461 ,556

E. T. L I METHOD AND APPARATUS FOR THE ELECTROLYTIC COATING OF METAL STRIP Filed April 1, 1943 6 Sheets-Sheet 2 IN VENTO K I fpw/v 7202/6,

Feb. 15, 1949. E. T. LORI G T v 2,461,556

METHOD AND APPARATUS FOR THE ELECTRQQYTIC COATING OF METAL STRIP Filed April 1. 194:s s She ets-Sheet :5

' I INVENTOR. [am/v 7.100

Feb.,15, 1949.

E. T. LORIG METHOD AND APPARATUS FOR THE ELECTROLYTIC COATING OF METAL STRIP Filed April 1, 1943 6 Sheets-Sheet 4 VIII/III] Q 7 I "INVENTORIY fflW/A 7f ZOE/6,

24/5 flrrae/vaf E. T. LORIG METHOD'AND APPARATUS FOR THE ELECTROLYTIC.

Feb. 15, 1949.

COATING OF METAL STRIP 6 Shee'ts-Sheet 5 Filed April 1, 1943 9""4 VIII mmvrbk flae/ aux Feb. 15, 1949; Y E T LORIG 2,461,556

METHOD AND APPARATU S FOR THE ELECTROLYTIC COATING OF METAL STRIP' Filed April 1, 1943 6 Sheets-Sheet 6 f0 22 ,ca /c*\ j I INVENTOR. Z6 v firm Z1006,

III I I I Patented Feb. 15, 1949 UNITED STATES M ETHOD AND APPARATU TROLYTIC CQATIN G QF METALSTRIR, v

Edwin "1. Long, Bellevue, fial'f as signor t C i- S=FOR rnn rnnnemagic-Illinois Steel Corporation, a corporation of New Jers Application April 1, 1943; sefial n 'S ClaimS; (cz'iisg ments for increased production ultimately have provided that the cathode be disposed in and out of the bath in a sinuous fashion, thus to. expose a greater amount of its linear extent and surface area to the electrolytic action in one plating tank. In this arrangement, instead of theanodes being placed above and below the cathode'as in the case of substantially horizontal operations, the anodes are suspended from bridges arranged across the electroplating tank so that they depend therefrom between adjacent courses of the sinuously-disposed base metal. If both sidespf the base metal are to be plated simultaneously in one operation, duplicate sets of anodesmust be provided so as to present effectiveanodic action closely adjacent theareas of the cathode that are to receive the coating. In some operations, the anodes for type of equipment have been made ,in slab Iprm, one for each bridge, which are of sufficient thickness to extend between the proximate faces of adjacent courses of base metal. In other cases, the anodes have been made in pairs, each of which serves an adjacent cathode surface. A further improvement has resulted from dividing the single slab type anodes, dependent from each-bridge, into a plurality of bar-like anodes similarly suspended. From this is derived a more uniform plating condition, since un-evenconsumption of the anodes may be corrected by replacing the --ones sustaining the greatest diminution in size.

Even though this last arrangement has proved far superior to all previous constructions, and is capable of providing satisfactory coatings, still, due to the great number of operating variables'entailed, many disadvantages remain which will now be discussed.

In electroplated coatings, the amount of coating deposited is dependent, among other things, upon the current density prevalent over any area of cathode surface under consideration, The current densities are determined by the amperage flowing in the system, and by the effective'circuit thei anodes -irgom", the, right-ha rightwardly) and the additiol fundamental,disadvantages flowing from the use of, a bar-.typeilor,slabatype,.anode,- since the current distribution isnot' uniform; thus effecting more rapidconsumption of somev of the anode surfacesthanother portions thereof. Such nonuniform consumption is effective to varythe spacing between the anodeandpathode surfaces, causing the resistance to vary accordingly, and, thus, altering the current densities sufficiently, to cause non-uniform deposits to occur. Except in carefully controlled systems, this results in streaky coatings, the difierences in the weight of which I across the sectionimay be readily observed by visual inspection. Q 7

- To prevent-this unsatisf wry rsult,{i ti's' necessary to shut downQthe, electroplating ,line at recurrent intervals for the purposeof 'removin -v h, a odes f P- i= 9 th t a been cqnsumedto the extent ofproviding too great aspaceb'tw'en the anode and cathode surfaces must be removed and replaced, manually. This. is. usually accomplish-ed by arranging the order of anode consumption so as to efiect most removals at one end of a bridge, and so as to make anode additions at the opposite ends of such bridges by sliding the anodes therealong to fill in the; blank file to make room for .thenew one. As between adjacent bridges, it is preferable that this be accomplished in opposite directions; that is, if one bridge'is servicedby theremoval of anodes from the. --left-hand,, end (thus necessitating the sliding of the intervening anodes leftwardlyi andbyitheaddition; amewf'a ode ,totheright hand en ;then,.en ge s,

thisis accomplished effecti the removal of necessitating of the ntervening anodes labor, and care must go into this result as the following facts and figures will demonstrate.

The trend is toward the use of cast anodes that are approximately 2 x 2 in cross-sectional area For the coating of the average 28 sheet, fourteen anodes to the bridge are required, it being understood that the effective anode surface is usually less wide than the cathode surface to assist in the reduction of heavy-edge plating. With sixteen bridges per line, there is thus required 224 anodes weighing approximately seventy pounds each. Since at 50% consumption the anodes fail to provide a sufficient plating condition, they must be changed at this stage and be replaced with new anodes. For the production of 3000 base boxes for each eight-hour-shift per line of one-half pound tinplate, the anode consumption is about forty-eight, averaging two width changes every eight hours, which, when multiplied by 16 (the number of bridges per line), involves sixty-four anodes per line every eight hours, or eight new anodes per hour. Since each anode that is replaced involves a used one and a new one, sixteen anodes must be handled each hour, or one every 3% minutes. The casting of new anodes for three production lines must be conducted, therefore, at the rate of 192 for every eight-hour operating period, or one anode every 2% minutes. great precision and with smoothness of surface, rendering high speed operations exceedingly difficult to maintain, and requiring the attendance of many proficient operators for the provision and maintenance of optimum operating conditions.

Alpart from the high cost attendant upon the necessary labor for the maintenance of the proper operating condition, other disadvantages attend the use of bar-type anodes. The electrolytic action is such as to cause the anodes to be consumed more rapidly at the bottom than at the top of the tank, which is reflected in a gradually tapering section that sometimes attains such thinness near the bottom of the anodes as to cause them to break off, whereby a lump of the plating metal will fall down between the strip and the guide-rolls, fouling the machinery, and renderin the resumption of satisfactory operating conditions impossible so long as the piece of metal stays there. Costly interruption in operations and considerable trouble distribution of the coating is possible by this method, since the heavy deposits of coating adjacent the edges do not fuse readily, and when fused are disposed to draw into globules destructive of the continuity of the coating, and present a dull, gray, streaky appearance which is not acceptable to the trade.

The present invention relates to a method and equipment designed to circumvent these and other disadvantages" by the use of a continuous anode disposed in relation to the cathodic base metal strip in a sinuous fashion comparable to the preferred disposition of the latter, as discussed above. One or more anodic strips, for the plating of one The anodes must be cast with or both surfaces of a base metal strip simultaneously, are contemplated, and the automatic features of control are such as to eliminate the operating variables and disadvantages discussed above, thereby to give rise to an operating optimum condition productive of a superior product and many related advantages.

It is, accordingly, an object of the present invention to provide an improved method and apparatus for electroplating elongated metal bodies continuously, so as to reduce operating variables and human error derived from manual control to negligible quantities.

It is another object to provide for electroplating under conditions in which a substantially constant distance between anodes and cathode is maintained throughout the greater portion of the time they are exposed to the electrolyte in plating relation. As a corollary object, it is provided that the anode and cathode surfaces shall be placed as closely as possible to each other without touching, thus to augment greatly the possible operating speeds for present commercial weights of coating, or greatly to increase the weight of coating for present commercial operating speeds.

It is still another object to effect the electroplating of metal upon metal under conditions which provide for substantially uniform current flow and density at all points between anode and cathode.

It is a further object to provide for the continuous and facile inspection of the anode and for the servicing thereof, without interrupting the electroplating operation to preserve the correct operating condition.

Another object is to increase anode consumption, and otherwise to provide for the more efficient utilization and handling of anodes.

It is another object to provide for the highspeed electroplating of strip with tin, or similar plating metal, at rates of linear flow in the order of 300 to 1400 feet per minute or more without sacrificing the uniformity and perfection of coating.

A further object is to eliminate the production of non-uniform coatings, especially heavy-edge coatings, by masking the anode and cathode strips to provide a selectively controllable coating gradient from central to edge portions of the strip, allowing the critical adjustment of the effective surface area of the anode in relation to the cathode, and by automatically maintaining this relationship, irrespective of extraneous movements.

It is a further and important object to provide for the automatic control of an electroplating operation in such a manner that unavoidable operating variables must be averaged throughout the transverse and linear extent of cathodes to re-- suit in uniform plating conditions in an automatic manner.

Other objects include a greatly improved. more eflicient method and apparatus for electroplating, whereby the disadvantages of present methods and equipment are overcome; including the prevention of burning and overheating of coatin s; the elimination of operating shutdowns usually attendant u'oon anode changes; and the great facilitation of anode formation, inspection, control, and maintenance.

The forego ng, as well as other objects and advantages not spec fically mentioned, will become apparent hereinafter when the following specificat on is read in conjunction with the accompanying drawings in which:

rigure "i represents a longitudinal, sectionalelevational view of one form of apparatus for platingone sideof a strip metal object in accordance with the present invention.

' FigureZ represents a corresponding view of apparatus similar to that of Figure 1 for use in conjunction-therewith to plate the opposite side of the same'strip metal object in accordance with one arrangement;

Figure 3 represents an enlarged plan view of electroplating apparatus similar to that shown in Figures 1 and 2, but with parts broken away, and with certain elaborations; added to show details of a preferred form of construction.

Figure 4 is a fragmentary, longitudinal, sectional-elevational view of the apparatus shown in Figure 3.

Figure 5 is a fragmentary, sectional-elevational view taken along lines V-V in Figure 4.

Figures 6 and 7 illustrate, in front elevational and sectional plan views, respectively, certain details of construction involved in the foregoing figures.

Figures 8, 9, 10, 11, and 11a disclose a modified form of anode, and its method of production, which may be used in accordance with the present invention.

Figures 12, 13, and 14 are, respectively, longitudinal sectional-elevational, sectional-end, and fragmentary plan views, with certain parts removed, illustrative of a modified form of the invention.

Figure 15 is a sectional detail view.

Referring in greater detail to the drawings in which like references refer to like parts through-- out:

The invention, as illustrated in Figures 1 and 2, comprises a pair of electroplating tanks and 2| which are adapted to sustain a level of liquid electrolyte 22. The tank 2|, representing the last in the sequence of electroplating operations; is provided with a partition or septum 23 defining a compartment 24 which is adapted to retain a level 25 of water, or other suitable rinsing liquid, for washing the coated article'as it leaves the electroplating baths.

A plurality of cathode rolls 26, in conjunction with the plurality of cathodic guide rolls 21, is

arranged to conduct a strip of base metal C sinuously in and out of the tank in a continuous manner. Similarly arranged is a plurality of anode rolls 28 which, in conjunction with stationary guides 29, serves to conduct a strip of plating metal A sinuously through the tank in a manner corresponding to the disposition of the cathode" strip C, and in substantial parallelism with the latter, although out of contact therewith. The guides 29 may also assume the form of rolls, although the space is more efiiciently utilized by adopting the half-moon construction illustrated. These guides are, preferably, composed of a composition that is inert towards the electrolytic solution, in relat on to which the strip slips quite easily by virtue of the lubricating properties of the electrolyte and the smoothness of the bear mgs.

The anode strip A may be provided in preformed lengths appropriately coiled for delivery to the system, or it may be continuously formed by the provision of a melting pct 30 having a water cooled casting orifice 3! adapted to congeal the molten metal contained in the pot just before it emerges from the latter. A short length of strip of higher melting point than the plating metal,--if inserted in the casting orifice before melting the plating metal; may' be empioyeri to used'anode stripjwhich is accumulated and returned to themeltingpot 30. In order to insure continuous operations, the last anode roll 28; at 'theanode exit end of the tank, may be provided with'a complementary driven roll 31, whichc'ooperates therewith to clamp the anode, andto efiectits continuous advance, even though the winding operation at the arbor 36"may be temporarily suspended to perinit'the stripping of coils from the arbor 36 The arrangements, as shown in the advancement of the anodic line.

in the apparatus in Figure 2, are identical with those describedabove, although oppositely disposed, whereby, since identical references have been employed, the one descriptionwill suflice for both.

It will be observed that the direction of flow of the anode strip A is opposite to that of the base metal being plated. In the case of tinplating operations, the anode strip may be cast of pure'tin, or may be supplied from a prefabricated tin strip of appropriatev width, in either case having an original thickness preferably of approximately Its rate of movement need be of a very low "order, such as one or two inches per minutefor: most .efiicient consumption. Even though it is contemplated that at least two-thirds of the anode will be consumed by the time it emerges atthe exit end of the tank, and, thus, will be one-eighth inch thick in the assumed example, it will still be possessed of sufi'icient strength to be pulled from the tank, and to assist Tin has sufficient tensile strength and ductility to withstand the'repeated bends throughout the tank without failure. It may be assisted in its course by differentially driving theanode rolls 28 in "such relation to the tension rolls 34 to afford tension close toithe elastic limit of the material, so as to insure the taut suspension and rigid, planar disposition of its several courses throughout the system toperfect their parallel arrangement with corresponding courses of the strip C. The cathode strip C representing the base meta1 to be coated, is likewise tensioned by tions of the vertical courses thereon In this respect, themost efficient plating condition is derived by having 'the anode andcathode as "close as possible without touching, although it will beapp reciated that variations in this distance are. not critical in so far as uniform thickness of plating is concerned.

The arrangements shown and described in these figures necessitate the plating of thecathcomplication of the construction is avoided, and

Thigh currentdensities, which tend to burn, melt,

or otherwise disfigure the coating, are avoided.

It is obvious, however, that, should it be desirable',,, uother continuous anode could be "'addedto'" one'tank' in a manner similar to those I mills, frequently have almost to plate bothsurfaces of In the avoidance of heavy edges, the anode strips A are preferably narrower than the oathode strip. In the case of the prefabricated coil of anode metal, suitable slitters may be provided in lieu of the rolls 33 to trim the anode to the requisite width in accommodation of the width of cathode being run. In this case, the metal removed by the slitters may be remelted, recast and rolled again into an anode strip. In the case of the continuous casting arrangement, the

casting orifice may be controlled to provide a strip of the necessary width, or slitters may be provided in the same manner as already described. To reduce to a certainty the manner of controlling heavy edges beyond that possible by these procedures last described, and to render the apparatus flexible in the treatment of various widths of strip, it is preferable to employ shields or masks 38 for disposition between the anode and the cathode to effect positive control thereof in a manner presently to be described.

By this latter arrangement, it is possible to fab ricate the anode strip at a width-that will ac 'commodate the widest cathode strip to be plated, and, then, to adapt the device to narrower width gauges by controlling the effective area of the anode by means of such shields or masks 38. This latter effect may be obtained 1 through the use of apparatus similar to that illustrated in Figures 3, 4, 5, 6 and 7, to which reference is now made.

The shields or masks 38 are preferably carried by a horizontal frame that is divided into two parallel parts '39 and 40, respectively, which are carried independently of the mountings of the anode and cathode rolls on or adjacent the tank itself by propelling screws 4| and, 42, each of which has rightward and leftward threaded portions 43 and 44, respectively. The propelling screws 4| and 42 are suitably journaled in stationary slide-bearings 45, mounted in any suitable way proximite to the electroplating tank, as on the tank itself, as illustrated in Figures 3 and 5. At one of their. ends, each of the shafts 4| and 42 may be provided with synchronized torque-imparting means, such as suitable gearing, or sprockets 46 and chain 41, which, through automatic or manual means 48, may be used to' turn the propelling screws simultaneously, so as to vary the spacing between the frame parts 39 and 4|], upon which thershields 38 are carried.

By this arrangement, any width of anode strip may be accommodated between the shields 3B,

and the effective area thereof may be varied by moving the supporting frames 39 and 40 farther apart, or closer together, as the case may be,

while preserving their parallel relationship.

It will be seen from the foregoing that the propelling screws act as centering devices for the frames 39 and 40, and for the individual shields 38 depending therefrom, so that, if a cathode strip of appropriate width were to. be conducted through the system, no further adjustment would be required so long as thestrip C traveled in a well-centeredpath. But such is not usually the case, since cathode strips, such as strip steel rolled on conventional hot and cold camber imparted thereto, whereby the longitudinal axis of the strip is not straight but curved, sometimes in one direction, sometimes imperceptible.

. .is presentin' an electroplating tank at. one time, by virtue of the serpentine course thatit is made strips, renderingit necessaryto correct for such condition,.- if perfectly uniform coatings are to be realized. The manner. inwhichthis is done will nowbe described.

-It has been said that the propelling screws 4| and 42 are effective in supporting the frames 39 and 40, and dependent shields 38, in-the;tank. Even-though, by revolving the propelling screws, the effective distance between the frames and shields may be varied, such adjustmentis not available tocause-the effective area of the anode to follow the strip in any of its departures from center. Since the width setting determinative of the correct relationship between anode and cathode areas is provided and maintained, it then becomes necessary to effect the movement of such setting to shift the effective anode area to agree with the placement of the cathode as it moves to a and fro crosswise of the tank. This is accomdirection. In this manner, as the strip 0. moves from one side to the other, the shafts may be moved a corresponding amount to preserve a well-centered. relationship. between the anode and the cathode, in so far as the effective area of the former is concerned, and this, even though the anode itself is not subject to transverse-movement. 1

' To insure that the propelling shafts, frames, and shields, are disposed accordingto the dispositionof the cathode strip, and theirmovement coordinated with those of the latter, an electriceye or photo-electric cell is fixedly arranged to scan a marginal portion of entering cathode strip C for response to the proportionality-of lightreflective surface, represented by the-strip, to the relatively dark surface of the underlying roll 26, whichmay be provided with-a blackened area for thispurpose. The photo-electric cell 50 is energized according to the relative degree of light derived from the strip within its scanning area, which light fluctuates as the striptracks back and forth.- The responses of the cell are" applied to control a reversible electric motor 5!, through a circuit (notshown), which, in turn, drives a pinion 52 through a reduction gear'53 critically to .movea, segmental gear Eeeither inclockwise or counter-clockwise direction, as'the case-maybe,

. depending-upon whether the strip has moved shafts 4| and 42,.respectively. As viewed in Figure .5, if the striprnoves leftwardly,=;more light will be reflected into the photo-electric cell 50,

which willcause the motor 5| to be actuated so as .to turn the pinion 52 in a clockwise direction,

as viewed in this figure. This drives the gear 54 and- 6 n, a et n- 0 swbediree mna hus and associated gearing and yokes, rightwardly a corresponding amount. Thus is the plating condition productive of the best coatin continuously maintained.

It is obvious from the foregoing that any of the well known electronic devices and circuits may be used in conjunction with the photo-electric cell for giving effect. to this result. Similarly, the photo-electric cell may be replaced by some other electrically-responsive device, such as, a solenoid with a tactile armature, as shown in Figure 15, for movement in response to the movement of the strip to vary the magnetic reluctance of its circuit, through which control and actuation of the motor is ultimately derived.

Figure 15 illustrates means suitable for effecting said regulation by the aforementioned tactile armature in conjunction with a solenoid. In Figure l5, numeral 66 designates the frame supporting the device; 61 is 'a grooved wheel engaging the moving strip C and adapted to be shifted thereby in a horizontal plane. Wheel 61 is rotatably mounted on one extremity of a shaft 68 which passes through a guide 69 to prevent rotation thereof in a vertical plane. The upper extremity of shaft 68 is secured to the inward extremity of bar Ill carrying thereon armature H, the bar being slidaby supported at both ends thereof by roller bearings 12. The outward extremity of bar 10 coacts with an inwardly-acting spring 13, adapted to maintain the assemblage of bar 10, armature H, shaft 68 and grooved wheel 61 in 2.10 to .provideaplating-current gradient adjacent the edges of the cathode to effect a, feathering of the coating applied to these portions so. as to balance the tendency towards heavy edges; The notches 380 preferably terminate in points, the apices of which fall in a line fat-or slightly beyond the edges of the cathode C, and in substantial parallelism to the paths of travel thereof. As viewed in Figure l, appropriate spacing 38d between'anode-edges and shield-sides is provided to allow for the reduction of the effective anode area inaccommodating cathode strips of narrower widths than those illustrated. Itiwill be appreciated that a'portion of the cathode stripC has been broken away from the view of Figure 6-to show the notches 38c, a1- .thoughthe disposition of the marginal portions of the'cathode stripiis indicated in thefragment of the strip shown at, the lower part of the view. In Figure 7,.cathode Chas been included in section.to.revealtherelationship of .parts. In practice, the spacing between anode and cathode need be no greater-than the thickness dimension of the notched i shield-member 385, although, to. eliminate frictional drag and to preclude possible damage to the coating,itis preferablethat slight spacing be maintained betweenthe movable and stationary parts. It will be appreciated that the carefully regulated tension-in .both. anode :and

control ofthe several'parts, in preservation-of this relationship, a relatively simple matter.

With a view toward increasing the efliciency of the anode, more rapid deposition of coating may be obtained by increasing theeffective'area of the latter, subjectto the 'conditions of control dein Figures 8 and "11, inclusive. An-anode' strip A may be prefabri'cated with its active surface sercontact with the edge of moving strip C. Armature H is surrounded by a solenoid l4 placed concentrically thereto at a distance to suit the desired electrical characteristics of the circuit:

Electric terminals l5'provide connection with the electric circuit employed and ultimately with the motor 5|. v 7

Contro effected by the device depends upon the relative displacement of armature H in re spect to solenoid 14. When strip C is in a neutral position, the electric circuit passing through solenoid M and electrical means auxiliary thereto is balanced, and motor 5! remains inactive. When .strip C moves leftwardly, wheel 61 and assemblage...

corresponding thereto is also'moved to the left, thereby changing the relative position of armature H and solenoid 14. Variation in magnetic reuctance corresponding thereto throws the circuit passing through solenoid 14 out of balance .and causes motor 5| to rotate in the direction to impart inward motion of yokes 56 and thus pulling shafts ll and 42 rightwardly. When cathodic strip C moves rightwardly, the reverse of the foregoing takes place.

Withreference to Figures 6 and '7, the relationship of the shield 38 to cathode C and anode A may be readily understood. lhe shields 38 are channel-shaped members of suitable dielectric material constructed to have a short leg 38a and a long leg 38b. The long leg 381) extends between the anode and the cathode, and defines the effective surface of the former. As shown in Figure6,

. the long legs of the shields 38 are provided with tapering notches 380 of suitable depth, which act rated in a manner toincrease the effective'surface area thereof. *In thecase of the prefabricated anodic strip, thismay be achieved inanysuitable manner, as by passing the strip 'betweenknurling rolls. In the case of the continuous casting device shown in'Figures land 2, this may be doneby making one of the pinch rolls 32; which withdraw the metal in solidified form from the casting'orifice 3|, with a corrugated or knurled surface, as shown at 32a in- Figure 8, which serves to impress the pattern upon the surface of the anode. This is illustrated in plan in Figure 10, while the correspondingside 'elevational view is illustrated in Figure 11. in Figure -9 the operating relation of such'an anode strip vA, in relation t'othe cathode strip C; isillustrated. Although the effect'of these serrations:isito varyt'he distance between the cathode andvan'ode -surfaces,.they lie transversely 'the'reof,-whereby their total effect is averaged over even if the. two were to move, inthesame direction,

the surface speeds of each; are so'different as to effect the. averaging of the platingcond1tion practically to the-same extent; ,Therelative proportions of the serrations to the anode strip are.sub-' ,ject to-Variation to suit the particular needsof a given 'setjof operating conditions, those shown v in thedr-awings being 'merelyjllustrative.

; The serrated surface ,of the anode A has the additional, function vof increasing its flexibility, permitting, its s uperfici al, mass s 1t P te-bsndieai ih9l ti rssing cathode strips makes: the precise disposition and hstan I? andtensioningthem beyond the-elastic .limit of thematerial tocause the anode to stretch unduly. Anotherma-nner for achieving this result without unduly weakening such an anode strip is shown in Figure 11A,wherein the anode A is illustrated as having 'substantially straight-sided. grooves disposed transversely thereacross when the anode lies in a straight path, which become closed on an inward bend, andfanned-outonan outward bend to prevent plastic flow of the metal. Any shape and disposition of groove, notch, or discontinuity of surface, as applied to either or both anode surfaces, is contemplated for this purpose.

The invention may be carried out by an alter-' nate anodic arrangement illustrated in Figures 12 to 14, whichmay be applied to coat oneside of a cathode strip, ifpreferred, but is particularly well adapted to the coating of both sides of the strip simultaneously withoutentailing a complex structure and congestion of parts. In this case the cathode strip isintroduced into the tank 20, andconducted backand forth over. cathode rolls 11,111 a mannersimilar to that already described. The anode, however, iscomposed of one or two strips (preferably .two)- which may be continuouslycast as used, or'prefabricated to form a roll of anode strip 6fl,-wh-ich is disposed on a horizontal axisof revolution to deliver two plies of anodestripv downwardly intothe tank 20 Y (see Figure-'12) The anode strips are passed around a cylindrical roll 6|, whose axis of revolution is maintainedat 2.45. degree angle, which serves to turn ,the direction of travelof the anode strips 96 degrees,-thus causing them to stand on end, with the planes of their major surfaces extending in the vertical.

;As viewed ln,Figure.,l4, itwillbe seen that the anode strips A are conducted in a serpentine fashionback-and-forth acrossthe tank by anode rolls 128, and are removed from the opposite end of the tankbymeansrof another oblique roller 62, guide ,roller .63, and boiler 64, in a. manner similarv to .their entry.; Small guide rolls; 6 5,are employed at the approach and exit ends of the tanks to as- =sist: in .introducing and, withdrawing: the anode- A strips to and fromthegtankw The anode rolls 28' are disposed in stag ered relation at opposite sides 1 of the. tank, and revolve, about vertical axes. Interrnediately of the tank, the anode. strips are divided by means of shields 38', which allows for -the-passageof= the cathode strip C, continuously between them.-- Inthis case, the divider shields 38 are of. channel-shape, with bothlegs of .the channel being of :thesame length, and provided with grading-notches 38c. These channel-shields 38' maybe stationary, or.may .be. mounted in a manner similar to those previously, described for movement towardand away from each other to accommodate different widths of cathode strip, and, coincidentally, to vary the:elf-ective area anode made available thereto. --The anode rolls 28- maybedriven in a manner to advance the anode stripsuunder. tension, thus to provide uniform spacing between cathode and anode surfaces and to giveefiect to the same optimum operating-conditions described hereinbefore. I In the modification shown in these figures, as 'in the preeedingconstruction, the cathodic strip 7, C is conducted through the tank at a relatively high rate of speed, while theanodic strip proceeds relatively slowly. 1Perforations (notshown) may be provided through the anode-strips to permit circulation of electrolyte, or the anodes may be of a foraminous construction. Another obvious modification of the various arrangements shown would be the rearrangement of the anodicand cathodic strips with respect to each other so that, in any embodiment, the anode would be where the cathode is, and vice versa. The adaptations necessary to effect such transposition are obvious and need no further elaboration.

From the foregoing it will be observed that the continuous anodes herein provided are constantly being renewed, wherebyvno defective portion that might occur along their length stays long enough in one position to make its presence manifest in the coating of the cathodic strip. In the first embodiment of the invention, in which the placement of travel of both the cathodes and anodes substantially agree, the anode is subject to continuous inspection at the point where it emerges from the bath, at which point it may be scraped and kept clean.

The foregoing arrangements will appear to those familiar with the problems in this field as satisfactory solutions to the principal operating difiiculties encountered in electroplating strip-like objects, the most important of which is the provision and maintenance of a uniform plating condition across the width of such objects all along the portions of their length that are exposed to electroplating action. At the same time, many alternative arrangements and modified constructions will suggest themselves which, though not specifically illustrated, will still be within the basic teaching of the present invention as recited in the claims. A few of these may be noted without attempting to exhaust the possibilities:

The prime requisite in realizing the benefits hereof resides in a continuous anode having an effective surface that presents anaverage uniform plating condition in relation to the cathode strip throughout the length thereof during plating. An anode, continuously presented and fed, may assume any one of a variety of forms to this end. Thus, a backing-strip or web of solid or foraminous material may be provided to carry the anodic metal, which may be cast thereon in fused condition, or prefabricated in bar or plate-like sections and afiixed thereto, or deposited in powder or granular form thereon and secured by fritting, sintering, soldering, or by mechanical means, such as a suitable adhesive or retaining fabric. Such carrier strip may be of dielectric material, in which case the plating current is caused to emit from one surface thereof only to increase the directional plating efiiciency. Also, if the dielectric carrier is suiiiciently bendable and is preformed to a sufiicient width in excess of the anode-width, per se, it may be folded overto over-lie edge portions of the effective surface area of the latter to accomplish a shielding function that would be operative for predetermined widths of cathode strip to the exclusion-of the adjustable shields 38.

The anode may assume the form of a reticular body in which filaments 0f plating metal are interwoven with each other for use in this form, or as a carrier fabric for the compartment of additional plating metal in powdered, fused, or massive form. Similarly, filaments of plating metal may be interwoven with filaments of dissimilar material that is either electrolytically inert or active, as desired, to enhance the flexibility or strength of the anode, or to provide for the deposition of polymetallic coatings in one operation, or both. Such a fabric, in which inert filaments were arranged with a view toward preventing heavy-edge plating, could be used to effect a coating-gradient to provide a uniformly-plated cathode. Therefore, whether the anode be a composite of articulated masses, a woven body, or a continuous strand, either with or without a carrier web, the primary purpose of the invention will be served.

The cathode may also consist of a metallic fabric; a plurality of elongated strips, each of relatively narrow width; or a multiplicity of sheets or plates articulated in any suitable manner for continuous presentation and advancement throughout an electroplating operation as here set forth.. Although all of. these alternates for both anode and cathode increase the complexity and cost of such operations, rendering the initially disclosed embodiments the preferred forms, still, they are deemed to be such reasonable modifications of the basic idea as clearly to fall within the purview of this invention.

It is not intended, therefore, that the invention be limited to the precise constructions illustrated, but that it be accorded a broader interpretation in conformance with the spirit of the accomplishments represented thereby, as is set down in the claims to follow.

I claim:

1. Electroplating apparatus comprising means for guiding a cathode strip through an electrolyte, means for guiding a strip anode in parallel, proximate relation to a cathode strip traversing said first-named means, shields extending between the edges of the cathode and anode strips, mountings for said shields adjustable transversely of the path of the cathode strip, a motor actuating said mountings and a control mechanism for said motor responsive to lateral shifting of the cathode strip.

2. The apparatus defined by claim 1 characterized by said control mechanism including a lightresponsive element activated by the position of an edge of said cathode strip.

3. In a method of plating a coating onto a base metal strip, the steps including passing the strip continuously through an electrolyte as a cathode, passing an anode in the form of a strip wider than the base metal strip continuously through the electrolyte, guiding the anode strip parallel to the base-metal strip and closely adjacent thereto, maintaining between the edges of the base-metal strip and the anode strip a shield having openings spaced therealong gradually diminishing in extent toward the edges of the base-metal strip, and.

automatically moving said shield transversely of the path of the strips on transverse shifting of the base-metal strip.

4. A method of electroplating strip-like objects continuously which includes: advancing such an object continuously through a bathof electrolyte as cathode; passing a strip-like anode continuously through the bath so that substantial portions of one of its surfaces fall closely adjacent areas of the strip-like object to be plated; interposing shielding means between portions of the adjacent areas of the strip-like anode and cathode to prevent heavy-edge plating on the latter; automatically shifting said shielding means transversely with respect to the direction of travel of said cathodic object to maintain a substantially centered relationship thereof continuously throughout the plating operation.

5. A method of electroplating which includes: advancing a strip-like cathode through an electrolytic cell; advancing a strip-like anode which is wider than the cathode coextensively with the cathode through at least a portion of. the latters path of travel through the cell; inserting masking means between the anode and cathode throughout the coextensive portions thereof so as to reduce the effective anode width to agree with the cathode width, and shifting said masking means transversely of the line of the cathode travel to maintain a. centered relationship between the eifectivecathode and anode surfaces at the coextensiveportions thereof.

EDWIN T. LORIG.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Certificate of Correction Patent No. 2,461,556 February 15, 1949.

EDWIN T. LORIG It is hereby certified that errors appear in the printed specification of the above numbered patent requiring correction as follows:

Column 4, line 16, for the word anodes read anode; column 6, line 58, after latter insert throughout; column 7, line 44, for proximite read proximate; column 9, line 67, for shield read shields column 10, line 6, after at strike out the hyphen; column 12, line 57, after anode strike out the hyphen; line 66, same column, for compartment read comportment;

and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Oflice.

Signed and sealed this 28th day of June, A. D. 1949.

THOMAS F. MURPHY,

Assistant Commissioner of Patents. 

